RUMINATION 281 Iii the upper jaw, and very usually there are none. As a general rule the third and fourth metacarpals and metatarsals become united to form a cannon bone. To this there is but one exception, the African Hyomoschu-s. Moreover, the second and fifth digits are nearly always rudimentary, and may practically disappear altogether. Here again the Tragululae are an excep- tion. The Jtumiiiantia are so-called on account of the fact that they " ruminate/* that is, after the food has been rapidly e FIG. 146.—Stomafh. of Ruminant opened to show the internal structure, a, Oesophagus ; li, rumen. ; c, reticttlum. ; df, psalterium ; e, at-omasum j fy duodenum. (After Flower and Lydekker.) swallowed, it is forced "back up the gullet and more thoroughly masticated. Associated with this is a complex stomach, which is divided into several compartments. This stomach has at least three compartments, as in the Tragulidae ; but it has -usually four. Its characters are illustrated in Fig. 146. The majority of the Selenodontia possess horns, which are partly formed of solid protuberances of the frontal bones. In the Giraffe they are somewhat different. This group may be divided into—A, TRAGULINA, Chevro- tains ; B. TYLOPODA, Camels, Lamas ; and G. PECORA, Deer, Ante- lopes, Oxen, Giraffes, Goats, Sheep. A. TRAGTJUNA. As the Tragulina are undoubtedly the xaosfc ancient of the Selenodontia it will be logical to commence with an account of them.